European Union foreign ministers have agreed to ban the import of Iranian oil as part of sanctions designed to pressure Iran to end its alleged pursuit of nuclear weapons.

The measures approved in Brussels include an immediate ban on the signing of new supply contracts for Iranian crude oil and petroleum products, with existing contracts being phased out by July 1.

Russia said it viewed the move as counterproductive and called for renewed talks between Iran and six global powers.

In a joint statement, U.S. Secretary of State Hillary Clinton and Treasury Secretary Timothy Geithner called the EU's decision "another strong step in the international effort to dramatically increase the pressure" on Tehran.

The EU currently buys around one-fifth of Iran's oil exports -- Iran’s most valuable asset. Negotiations are currently ongoing with several countries, including Saudi Arabia, to replace the Iranian imports.

Reports said additional restrictions on Iran's central bank also had been agreed. The ministers also agreed to ban trade in gold, precious metals, and diamonds with the regime and froze assets of three more people and eight entities, mostly in the transport sector.

British Foreign Secretary William Hague said the measures were part of "an unprecedented set of sanctions."

"I think this shows the resolve of the European Union on this issue and of the international community," Hague said. "It is absolutely right to do this in view of Iran's continued breach of UN Security Council resolutions and its refusal to come to meaningful negotiations on the nuclear program."

Australian Foreign Minister Kevin Rudd announced on January 24 that his country would follow the EU lead and ban Iran oil imports.

Israeli Prime Minister Benjamin Netanyahu, whose country regards Iran's nuclear program as a possible existential threat, praised the new EU sanctions but said it was difficult to know what their result would be. He urged “heavy and swift pressure” on Iran, saying “the sanctions must be evaluated according to their results."

"The European Union today decided to place sanctions on oil exports from Iran. I think this is a step in the right direction," Netanyanu. "For now, it is impossible to know what the result of these sanctions will be, but heavy and swift pressure is needed on Iran. These sanctions must be evaluated according to the results they will bring. Today, Iran continues to develop nuclear weapons with no disruption."

International Atomic Energy Agency (IAEA) Director General Yukiya Amano meanwhile announced that it will send a mission to Iran that "is going to Iran in a constructive spirit, and we trust that Iran will work with us in that same spirit," according to an IAEA statement.

The team will reportedly be in Iran from January 29 to January 31 to "resolve all outstanding substantive issues" regarding the possible military applications of Iran's program.

'Twin-Track Approach'

EU foreign policy chief Catherine Ashton has said sanctions were designed to persuade Iran to return to talks on its nuclear program that Western powers fear is aimed at producing atomic weapons.

"We will be discussing and finalizing additional sanctions [on Iran], particularly focused on the central bank and on oil exports," Ashton said. "But I do want to, again, reiterate that this is part of trying to get a twin-track approach. The pressure of sanctions is designed to try and make sure that Iran takes seriously our request to come to the table and meet."

A speed boat passes by oil docks at the Iranian port of Kalantari in the city of Chabahar, east of the Strait of Hormuz, on January 17.

Ashton said world powers had yet to receive a reply from Tehran to an offer in October to hold new talks.

German Foreign Minister Guido Westerwelle said it was critical that action against Iran be taken, saying it was not a question of security in the region alone, but "a question of security in the world."

Iranian officials, however, remained defiant, with a member of parliament's energy commission, Ali Adyani, saying oil sanctions “will not have any effect on Iran's economy."